Transcript ppt - eweb.furman.edu

DIVERSITY OF LIFE
I.
Origin of Life Hypotheses
A. Three Primary Attributes:
- Barrier (phospholipid membrane)
- Metabolism (reaction pathways)
- Genetic System
- Barrier (phospholipid membrane)
- form spontaneously in aqueous solutions
Metabolic Pathways
- problem:
how can pathways with useless intermediates evolve?
A
B
C
D
How do you get from A to E, if B, C, and D are non-functional?
E
Metabolic Pathways
- Solution - reverse evolution
A
B
C
D
E
Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env.
E
Metabolic Pathways
- Solution - reverse evolution
suppose E is a useful molecule, initially available in the env.
As protocells gobble it up, the concentration drops.
E
Metabolic Pathways
- Solution - reverse evolution
D
Anything that can absorb something else (D) and MAKE E is
at a selective advantage...
E
Metabolic Pathways
- Solution - reverse evolution
D
Anything that can absorb something else (D) and MAKE E is
at a selective advantage...
but over time, D may drop in concentration...
E
Metabolic Pathways
- Solution - reverse evolution
C
D
So, anything that can absorb C and then make D and E will
be selected for...
E
Metabolic Pathways
- Solution - reverse evolution
A
B
C
D
and so on until a complete pathway
evolves.
E
Genetic Systems
- conundrum... which came first, DNA or the proteins they
encode?
DNA
RNA
(m, r, t)
protein
Genetic Systems
- conundrum... which came first, DNA or the proteins they
encode?
DNA
DNA stores info, but proteins
are the metabolic catalysts...
RNA
(m, r, t)
protein
Genetic Systems
- conundrum... which came first, DNA or the proteins they
encode?
- Ribozymes
info storage AND
cataylic ability
Genetic Systems
- conundrum... which came first, DNA or the proteins they
encode?
- Ribozymes
- Self replicating molecules
- three stage hypothesis
Stage 1: Self-replicating
RNA evolves
RNA
Stage 1: Self-replicating
RNA evolves
RNA
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 2: RNA molecules interact to produce proteins... if these
proteins assist replication (enzymes), then THIS RNA will have a
selective (replication/reproductive) advantage... chemical selection.
DNA
Reverse
transcriptases
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA;
existing replication enzymes replicate the DNA and transcribe RNA.
Can this happen? Are their organisms that read DNA
and make RNA?
Can this happen? Are their organisms that read DNA
and make RNA?
yes - retroviruses....
DNA
m- , r- , and t- RNA
Already have enzymes
that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA;
existing replication enzymes replicate the DNA and transcribe RNA.
DNA
m- , r- , and t- RNA
Already have enzymes
that can make RNA...
PROTEINS
(REPLICATION ENZYMES)
Stage 3: Mutations create new proteins that read RNA and make DNA;
existing replication enzymes replicate the DNA and transcribe RNA.
DNA
This is adaptive because
the two-step process is
more productive, and DNA
is more stable (less prone
to mutation).
m- , r- , and t- RNA
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of
replicating the RNA...
DNA
m- , r- , and t- RNA
This is adaptive because
the two-step process is
more productive, and DNA
is more stable (less prone
to mutation).
And that's the system we
have today....
PROTEINS
(REPLICATION ENZYMES)
Stage 4: Mutations create new proteins that replicate the DNA instead of
replicating the RNA...
DIVERSITY OF LIFE
I.
Origin of Life Hypotheses
II.
Early Life
- the first cells were probably
heterotrophs that simply absorbed
nutrients and ATP from the
environment.
- as these substances became rare,
there was strong selection for cells
that could manufacture their own
energy storage molecules.
- the most primitive cells are
methanogens, but these are NOT
the oldest fossils.
II. Early Life
- the second type of cells were probably like green-sulphur bacteria,
which used H2S as an electron donor, in the presence of sunlight, to
photosynthesize.
II. Early Life
- the evolution of oxygenic photosynthesis was MAJOR. It allowed life
to exploit more habitats, and it produced a powerful oxidating agent!
These stromatolites, which date to > 3 bya are microbial communities.
II. Early Life
- about 2.3-1.8 bya, the concentration of oxygen began to increase in
the ocean and oxidize eroded materials minerals... deposited as
'banded iron formations'.
II. Early Life
- 2.0-1.7 bya - evolution of eukaryotes.... endosymbiosis.
II. Early Life
Relationships among life forms - deep ancestry and the last "concestor"
II. Early Life
Woese - r-RNA analyses reveal a
deep divide within the bacteria
DIVERSITY OF LIFE
I.
Origin of Life Hypotheses
II. Early Life
III. Bacteria and Archaea
4.5 bya
3.5-8 bya
2.3
1.7
DIVERSITY OF LIFE
I.
Origin of Life Hypotheses
II. Early Life
III. Bacteria and Archaea
4.5 bya
3.5-8 bya
2.3
1.7
For ½ of life’s history, life was exclusively bacterial.
Bacterial producers, consumers, and decomposers.
DIVERSITY OF LIFE
I.
Origin of Life Hypotheses
II. Early Life
III. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
A. Oxygen Demand
all eukaryotes require oxygen.
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
A. Oxygen Demand
all eukaryotes require oxygen.
bacteria show greater variability:
- obligate anaerobes - die in presence of O2
- aerotolerant - don't die, but don't use O2
- facultative aerobes - can use O2, but don't need it
- obligate aerobes - require O2 to live
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
A. Oxygen Demand
all eukaryotes require oxygen.
bacteria show greater variability:
- obligate anaerobes - die in presence of O2
represents an interesting
continuum, perhaps
- aerotolerant - don't die, but don't use O2
correlating with the
- facultative aerobes - can use O2, but don't need it
presence of O2 in the
atmosphere.
- obligate aerobes - require O2 to live
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
B. Nutritional Categories:
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
B. Nutritional Categories:
- chemolithotrophs: use inorganics (H2S, etc.) as electron
donors for electron transport chains and use energy to fix carbon dioxide. Only
done by bacteria.
- photoheterotrophs: use light as source of energy, but harvest
organics from environment. Only done by bacteria.
- photoautotrophs: use light as source of energy, and use this
energy to fix carbon dioxide. bacteria and some eukaryotes.
- chemoheterotrophs: get energy and carbon from organics
they consume. bacteria and some eukaryotes.
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
C. Their Ecological Importance
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
C. Their Ecological Importance
- major photosynthetic contributors (with protists and plants)
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
C. Their Ecological Importance
- major photosynthetic contributors (with protists and plants)
- the only organisms that fix nitrogen into biologically useful
forms that can be absorbed by plants.
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
C. Their Ecological Importance
- major photosynthetic contributors (with protists and plants)
- the only organisms that fix nitrogen into biologically useful
forms that can be absorbed by plants.
- primary decomposers (with fungi)
II. Bacteria and Archaea
The key thing about bacteria is their metabolic diversity. Although they
didn't radiate much morphologically (spheres, rod, spirals), they DID radiate
metabolically. As a group, they are the most metabolically diverse group of
organisms.
C. Their Ecological Importance
- major photosynthetic contributors (with protists and plants)
- the only organisms that fix nitrogen into biologically useful
forms that can be absorbed by plants.
- primary decomposers (with fungi)
- pathogens
The Diversity of Life
III. Domain Eukarya
Protists are single celled or colonial organisms… they are the most primitive
eukaryotes, and they probably evolved by endosymbiotic interactions among
different types of “bacteria”
The Diversity of Life
III. Domain Eukarya
From different types of
protists evolved different
types of multicellular
eukaryotes: the fungi,
plants, and animals.
The Diversity of Life
III. Domain Eukarya
A. Protist Diversity
- green alga
Same chlorophyll as
plants
alternation of
generation
genetic analysis
confirms relatedness
The Diversity of Life
III. Domain Eukarya
A. Protist Diversity
- Choanoflagellates
The Diversity of Life
III. Domain Eukarya
B. Kingdom Fungi
- Decomposers
- Pathogens
- Excrete digestive
enzymes and absorb the
nutrients
C. Plants
1. Evolutionary History
Green Algal “roots” – Ulva (sea lettuce)
C. Plants
1. Evolutionary History
1. Green Algal “roots” – Ulva (sea lettuce)
2. Colonization of Land: Environmental Diff’s
Aquatic Habitats
Terrestrial
Water available
Desiccating
Sunlight absorbed
Sunlight available
Nutrients at Depth
Nutrients available
Buoyant
Less Supportive
Low oxygen, higher CO2 reverse
C. Plants
1. Evolutionary History
2. Diversity
2. Diversity
a. Non-Vascular (no true xylem or phloem)
Example: Mosses
2. Plant Diversity
a. Non-Vascular (no true xylem or phloem)
b. Non-seed vascular (club mosses, ferns)
2. Plant Diversity
a. Non-Vascular (no true xylem or phloem)
b. Non-seed vascular (club mosses, ferns)
- dominated swamps 350 mya – coal reserves
2. Plant Diversity
a. Non-Vascular (no true xylem or phloem)
b. Non-seed vascular (club mosses, ferns)
- dominated swamps 350 mya – coal reserves
2. Plant Diversity
a. Non-Vascular (no true xylem or phloem)
b. Non-seed vascular (club mosses, ferns)
- dominated swamps 350 mya – coal reserves
c. Vascular Seed Plants
a. Gymnosperms – “naked seed”
1. Evolutionary History
- dominated during Permian (280 mya)
and through Mesozoic, and still
dominate in dry env. Today
(high latitudes, sandy soils)
Gymnosperm
Life Cycle
2. Plant Diversity
a. Non-Vascular (no true xylem or phloem)
b. Non-seed vascular (club mosses, ferns)
- dominated swamps 350 mya – coal reserves
c. Vascular Seed Plants
a. Gymnosperms – “naked seed”
b. Angiosperms – flowering plants
all other plants – grasses, oaks, maples, lilies, etc.
- flower – attract pollinators
- fruit – attract dispersers
D. Kingdom Animalia
1. Introduction
a. Characteristics:
Eukaryotic
Multicellular
Heterotrophic
Lack cell walls.
D. Kingdom Animalia
1. Introduction
a. Characteristics
b. History
- first animals in fossil record date to 900 mya
largely wormlike soft-bodied organisms
D. Kingdom Animalia
1. Introduction
a. Characteristics
b. History
- first animals in fossil record date to 900 mya
largely wormlike soft-bodied organisms
- in the Cambrian, 550 mya:
– radiation of predators (Cnidarians)
– radiation of major phyla
organisms with hard parts
D. Kingdom Animalia
1. Introduction
a. Characteristics
b. History
c. Diversity
- Approximately 1 million described
animal species. Of these:
5% have a backbone (vertebrates)
( a subphylum in the phylum Chordata)
85% are Arthropods
D. Kingdom Animalia
1. Introduction
a. Characteristics
b. History
c. Diversity
d. Evolutionary Trends
1. Body Symmetry
asymmetrical
radially symmetrical
bilaterally symmetrical – evolving a head
D. Kingdom Animalia
A. Introduction
1. Characteristics
2. History
3. Diversity
4. Evolutionary Trends
a. Body Symmetry
b. Embryological development
zygote – morula – blastula – gastrula
D. Kingdom Animalia
1. Introduction
a. Characteristics
b. History
c. Diversity
d. Evolutionary Trends
e. Phylogeny
e. Phylogeny
2. Phylum Porifera: Sponges
- asymmetrical
- no true tissues, but cell specialization
Choanocytes are similar
to the free-living protist
choanoflagellates
3. Phylum Cnidaria:
Radial symmetry
Two tissues – endo and ectoderm
Sac-like gut
Diffuse nervous system (no head)
Hydra, jellyfish, anemones, coral
4. Bilaterally Symmetrical Animals
1. Protostomes – blastopore forms mouth
a. Lophotrochozoans
- Platyhelminthes
- Annelida
- Mollusca
b. Ecdysozoans
- Nematoda
- Arthropod Phyla
2. Deuterostomes – blastopore forms anus
- Echinodermata
- Hemichordata
- Chordata
- cephalochordates
- urochordates
- vertebrates
“Lophotrochozoans”
Phylum Platyhelminthes: “Flatworms”
-Bilateral symmetry
-Sac-like gut
-Ameobocytes like sponges
- planarians, flukes, tapeworms
Phylum Annelida – “segmented worms”
- bilaterally symmetrical
- cephalization (“brains”)
- repeated segments
- complete digestive ‘tract’ – one way gut
- polychaetes, earthworms, leeches
Phylum Mollusca: “molluscs”
- bilaterally symmetrical
- segmented body
- shell, can be ‘reduced’ or lost
- cephalization correlates with activity
- chitons, snails, bivalves, cephalopods
“Ecdysozoans”
Phylum Nematoda: “round worms”
- molt cuticle
- complete digestive tract
- some cephalization with anterior neural ganglion
- free living and parasitic
- human parasites: trichinosis, filariasis, elephantiasis,
Ascariasis (two foot intestinal worms)
Arthropod Phyla:
- Segmented body, jointed legs
- thick exoskeleton
-multiplication…specialization…fusion
- trilobites (extinct)
-Chelicerates (spiders, scorpions, horseshoe crabs, mites, ticks)
-Myriapods (millipedes and centipedes)
-Crustaceans (crabs, shrimp, lobster)
-Insects
“Deuterostomes”
Phylum Echinodermata – “echinoderms”
- still bilateral
- internal skeleton
- herbivores and predators
Phylum Hemichordata – “acorn worms”
- notochrod for support
- hollow dorsal nerve tube (“spinal cord”)
Cephalochordates – “lancelets”
Phylum Chordata: “chordates”
- notochord – a rigid supporting rod
- Hollow dorsal nerve tube
- Pharyngeal gill slits
- Post-anal tail
Urochordates – “tunicates”
Vertebrates: fish, amphibians,
reptiles, birds, mammals